Method and system for performing distance measuring and direction finding using ultrawide bandwidth transmissions

ABSTRACT

An identification tag is provided in which radio frequency (RF) circuitry and ultrawide bandwidth (UWB) circuitry are both provided on the same tag, along with some UWB-RF interface circuitry. The RF circuitry is used to detect when the identification tag must be accessed, and is used to connect the UWB circuitry with a power supply. The UWB circuitry then performs the necessary communication functions with a distant device and the power supply is again disconnected. In this way the power supply is only accessed when the UWB circuitry is needed and it&#39;s usable lifetime can be maximized.

CROSS-REFERENCE TO RELATED PATENT DOCUMENTS

[0001] This application is a continuation-in-part of U.S. applicationSer. Nos. 09/209,460, for “ULTRA WIDE BANDWIDTH SPREAD-SPECTRUMCOMMUNICATION,” filed Dec. 11, 1998; 09/685,202, for “METHOD AND SYSTEMFOR ENABLING DEVICE FUNCTIONS BASED ON DISTANCE INFORMATION,” filed Oct.10, 2000; and 10/214,183, for “MODE CONTROLLER FOR SIGNAL ACQUISITIONAND TRACKING IN AN ULTRA WIDEBAND COMMUNICATION SYSTEM, filed Aug. 8,2002, all of which are incorporated by reference in their entirety. Thisapplication relies for priority on U.S. provisional application No.60/339,372, for “METHOD AND SYSTEM FOR PERFORMING DISTANCE MEASURING ANDDIRECTION FINDING USING ULTRAWIDE BANDWIDTH TRANSMISSIONS,” filed Dec.13, 2001, which is incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] The present invention relates to radio frequency (RF)communication receivers, systems and methods employing ultra widebandwidth (UWB) signaling techniques. More particularly, the presentinvention relates to the systems and methods that use UWB transmissionsto track the movement of remote devices by determining those devices'movement, direction, and distance with respect to a central device. Evenmore particularly, the present invention relates to systems and methodsthat use both RF transmissions and UWB transmissions in the same device.

[0003] It is desirable in many environments to be able to monitor thelocation or movement of a remote device from a fixed local device. Forexample, retail stores may wish to monitor their merchandise; warehousesor cargo transports may wish to keep closer track of the cargo that theyhandle; and internal communications networks may wish to keep track ofwhat users are in which location. Thus, a variety of devices have beenused to determine location and distance.

[0004] An example of such a device is an RF identity tag, e.g., asdescribed in U.S. Pat. No. 5,995,006, to Walsh, U.S. Pat. No. 6,107,910,to Nysen, or devices of a similar design. Such an RF identity tag has RFcircuitry that can detect RF signals transmitted by a local device(whether fixed or mobile) and can then reply with an RF signal of itsown to send information back to the local device. The RF signal in thiscase is a data signal modulated by being impressed upon another RFcarrier signal.

[0005] The present inventors have also presented a system and method forusing UWB signals to achieve similar functions, as set forth in U.S.Pat. No. 09/685,202, for “METHOD AND SYSTEM FOR ENABLING DEVICEFUNCTIONS BASED ON DISTANCE INFORMATION,” filed Oct. 10, 2000. The UWBsignal in this case is preferably one that approximately matches itsbandwidth to its center frequency, as defined below.

[0006] One important aspect of remote devices such as these is theiruseful lifetime. If a receiver is used in a remote device, the devicemay have a limited power supply, e.g., a battery. In this case, it isdesirable to minimize the use of the power source so as to extend itsusable lifetime.

[0007] Some RF tags operate without a separate power supply. Insteadthey use the RF signal they receive to power themselves up and performtheir desired function, e.g., having the incoming RF signal charge acapacitor. This is not possible with current UWB designs. While UWBtransceivers may use low amounts of power they cannot use a power sourcecapacitively charged by an incoming RF signal. However, the UWB tagsproposed by the current inventors offer better reliability in clutteredenvironment, as well as other significant advantages.

[0008] It would therefore be desirable to provide a system that includesthe advantages of both designs, while limiting their limitations.

SUMMARY OF THE INVENTION

[0009] Consistent with the title of this section, only a briefdescription of selected features of the present invention is nowpresented. A more complete description of the present invention is thesubject of this entire document.

[0010] An object of the present invention is to provide a remote devicethat can receive information from a local device and perform a desiredfunction in response, e.g., sending a return signal with a maximumreliability and a minimum use of power.

[0011] Another object of the present invention is to maximize thecoordination of RF and UWB elements used in a single remote device.

[0012] Another feature of the present invention is to address theabove-identified and other deficiencies of conventional communicationssystems and methods.

[0013] These and other objects are accomplished by way of a remotedevice configured to receive both RF and UWB transmissions. Whileseveral embodiments are disclosed herein, one embodiment would be toinclude RF circuitry to receive an RF signal, UWB circuitry to transmita UWB signal, and a UWB-RF interface to facilitate communication betweenthese two elements.

[0014] In an effort to achieve these goals a combined ultrawidebandwidth-radio frequency (UWB-RF) remote identification tag isprovided, which comprises: ultrawide bandwidth (UWB) circuitry forreceiving or transmitting UWB signals; radio frequency (RF) circuitryfor receiving or transmitting RF signals; and interface circuitry formedbetween the RF circuitry and the UWB circuitry.

[0015] This combined UWB-RF remote identification tag may furthercomprise: a power supply for providing power to the UWB circuitry; and aswitch connected between the power supply and the UWB circuitry. Theinterface circuitry preferably controls the operation of the switchbased on a signal received from the RF circuitry.

[0016] The UWB-RF interface may further comprise a first scaler forreceiving a frequency signal from the RF circuitry, scaling it by afirst scaling factor N/M, and providing a first scaled frequency to theUWB circuitry. In this case N and M are preferably integers.

[0017] The combined UWB-RF remote identification tag may furthercomprise: a power supply for providing power to the UWB circuitry; and aswitch connected between the power supply and the UWB circuitry. Theinterface circuitry preferably controls the operation of the switchbased on a signal received from the RF circuitry. The scaled frequencyis preferably used by the UWB circuitry as a pulse repetition frequency.

[0018] The UWB-RF interface may further comprise: a second scaler forreceiving the frequency signal from the RF circuitry, scaling it by asecond scaling factor P/Q, and providing a second scaled frequency tothe UWB circuitry; a memory device for providing a data signal; and amixer for mixing the second scaled frequency with the data signal toform a UWB radio frequency signal. In this design P and Q are preferablyintegers.

[0019] The UWB-RF interface may further comprise all of: a first scalerfor receiving a frequency signal from the RF circuitry, scaling it by afirst scaling factor N/M, and providing a first scaled frequency to theUWB circuitry; a second scaler for receiving the frequency signal fromthe RF circuitry, scaling it by a second scaling factor P/Q, andproviding a second scaled frequency to the UWB circuitry; a memorydevice for providing a data signal; and a mixer for mixing the secondscaled frequency with the data signal to form a UWB radio frequencysignal, and providing the UWB radio frequency signal to the UWBcircuitry. In this design N, M, P and Q are all preferably integers.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] A more complete appreciation of the invention and its manyattendant advantages will be readily obtained as it becomes betterunderstood with reference to the following detailed description whenconsidered in connection with the accompanying drawings, in which:

[0021]FIG. 1 is a block diagram of an ultra-wide band (UWB) systemaccording to a preferred embodiment of the present invention;

[0022]FIG. 2 is a block diagram of an ultra-wide band (UWB) transceiveraccording to a preferred embodiment of the present invention;

[0023]FIG. 3 illustrates a processor system according to a preferredembodiment of the present invention;

[0024]FIG. 4 is a diagram depicting the interconnection of devicesaccording to a preferred embodiment of the present invention;

[0025]FIG. 5 is a flow chart describing a process for communicating withremote wireless devices based on distance information according to apreferred embodiment of the present invention;

[0026]FIG. 6 is a flow chart describing the process of establishing alink with remote devices using a multiple access protocol according to apreferred embodiment of the present invention;

[0027]FIG. 7 is a flow chart describing the process of determiningdistance to a remote device according to a preferred embodiment of thepresent invention;

[0028]FIGS. 8 and 9 describe alternative processes for communicatingwith remote devices based on distance information in accordance withother preferred embodiments of the present invention;

[0029]FIGS. 10 and 11 describe an alternative process for communicatingwith remote devices based on distance information in accordance withother preferred embodiments of the present invention;

[0030]FIG. 12 describes a process for providing secured communicationswith remote devices according to a preferred embodiment of the presentinvention;

[0031]FIG. 13 is a flow chart that describes an exemplary process forproviding a secured communications link using public key cryptography inaccordance with a preferred embodiment of the present invention;

[0032]FIG. 14 is a block diagram of a remote device according to apreferred embodiment of the present invention;

[0033]FIG. 15 is a block diagram of a remote device according to anotherpreferred embodiment of the present invention;

[0034]FIG. 16 is a block diagram of a remote device according to yetanother preferred embodiment of the present invention;

[0035]FIG. 17 is a block diagram showing a combined UWB-RF tag accordingto a first preferred embodiment;

[0036]FIG. 18 is a block diagram showing a combined UWB-RF tag accordingto a second preferred embodiment;

[0037]FIG. 19 is a block diagram showing a combined UWB-RF tag accordingto a third preferred embodiment;

[0038]FIG. 20 is a block diagram showing a combined UWB-RF tag accordingto a fourth preferred embodiment;

[0039]FIG. 21 is a block diagram showing a combined UWB-RF tag accordingto a fifth preferred embodiment;

[0040]FIG. 22 is a block diagram showing a combined UWB-RF tag accordingto a sixth preferred embodiment;

[0041]FIGS. 23A to 23C are signal graphs showing an embodiment in whichpulse position modulation (PPM) is used to make a UWB signal coherentwith an RF signal; and

[0042]FIGS. 24A to 24C are signal graphs showing an embodiment in whichbi-phase modulation is used to make a UWB signal coherent with an RFsignal.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0043] Preferred embodiments of the present invention will now bedescribed with reference to the drawings. Throughout the several views,like reference numerals designate identical or corresponding parts.

[0044]FIG. 1 is a block diagram of an ultra-wide band (UWB) systemaccording to a preferred embodiment of the present invention. As shownin FIG. 1, the UWB system 100 includes an antenna 105, a switch 110, anRF physical medium device (PMD) 120, a digital PMD 130, a physical (PHY)layer conversion protocol (PLCP) 140, a media access controller (MAC)150, a host controller 160, a MAC manager 170, a PHY layer manager 175,and an electronic device 180. The RF PMD 120 further includes a receiverfront end 122, a demodulator 124, a transmitter front end 126, and amodulator 128, while the digital PMD 130 further includes a receiverbaseband 132, a transmitter baseband 134, and a timing controller 136.The device 180 may include an application layer 185 that allows thedevice to operate in connection with the host controller 160 and a user190.

[0045] Although a single antenna 105 is shown that switches betweentransmitting and receiving, individual receiving and transmittingantennas may be used in alternate embodiments.

[0046] When the UWB system 100 is receiving a signal, the antenna 105converts an incoming UWB electromagnetic waveform into an electricalsignal (or optical signal) and provides this signal to the switch 110.In a receiving mode the switch 110 is connected to the receiver frontend 122 in the RF PMD 120, which performs analog signal processing onthe incoming signal. Depending on the type of waveform, the receiverfront end 122 processes the electrical (or optical) signals so that thelevel of the signal and spectral components of the signal are suitablefor processing in the demodulator 124. This processing may includespectral shaping, such as a matched filtering, partially matchedfiltering, simple roll-off, etc.

[0047] The received signal is then passed from the receiver front end122 through the demodulator 124 and the receiver baseband 132 for signalprocessing to extract the information from the incoming signal. Thedemodulator 124 performs analog signal processing on the incoming RFsignal, which is then converted (preferably by either the demodulator124 or the receiver baseband 132) for digital processing by the receiverbaseband 132.

[0048] The information extracted from the incoming signal is then sentfrom the receiver baseband 132 to the PLCP 140 to convert it to properformat for the MAC 150. Timing information from the incoming signal (orfrom a signal output from the demodulator 124) is received by the timingcontroller 136 and is sent back to timing generators in the demodulator124 and the modulator 128. (See FIG. 2 and related discussion.)

[0049] The MAC 150 serves as an interface between the UWB wirelesscommunication functions implemented by both the RF PMD 120 and thedigital PMD and the application layer 185 that uses the UWBcommunications channel for exchanging data with the device 180. The MAC150 is preferably a processor-based unit that is implemented either withhard-wired logic, such as in one or more application specific integratedcircuits (ASICs) or in one or more programmable processors.

[0050] The host controller 160 operates as an interface between the MAC150 and the device 180, and provides instructions to the RF PMD 120, thedigital PMD 130, the PLCP 140 and the MAC 150 through the MAC manager170 and the PHY layer manager 175. In this embodiment the hostcontroller 160 is shown as being separate from the device 180. Inalternate embodiments all or part of the host controller 160 can beplaced in the device 180.

[0051]FIG. 2 is a more detailed block diagram of the UWB transceiver ofFIG. 1. As shown in FIG. 2, the UWB transceiver includes an antenna 105,a transmit/receive (T/R) switch 110, a receiver front end 122, atransmitter front end 126, a demodulator 124, a modulator 128, and adigital PMD 130. The demodulator 124 includes a splitter 210, aplurality of correlators 220 ₁-220 _(N), and a plurality of input timinggenerators 825 ₁-825 _(N). The modulator 128 includes an output timinggenerator 205 ₀, an encoder 225, and a waveform generator 230. In thisembodiment the output timing generator 205 ₀ and the plurality of inputtiming generators 205 ₁-205 _(N) are formed together into a singletiming generator module 205. This embodiment allows multiple fingers(also called arms) to process the incoming signal at the same time,increasing the speed and efficiency of acquisition and tracking.

[0052] The T/R switch 110 connects the antenna 105 to either thereceiver front end 122, or the transmitter front end 126, depending uponwhether the transceiver is transmitting or receiving. In alternateembodiments separate transmitting and receiving antennas could be used.

[0053] When receiving energy through the antenna 105, the receivedenergy is coupled in to the T/R switch 110, which passes the energy tothe receiver front end 122 as an incoming signal. The receiver front end122 filters, extracts noise, and adjusts the amplitude of the incomingsignal before providing the same to the splitter 210 in the demodulator124.

[0054] The splitter 210 divides the incoming signal up into N copies ofthe incoming signal and applies the N incoming signals to respectivecorrelators 220 ₁-220 _(N). Each of the correlators 220 ₁-220 _(N)receives a clock input signal from a respective input timing generator205 ₁-205 _(N) of the timing generator module 205 as shown in FIG. 2.Each of these correlators corresponds to a different finger of thetransceiver.

[0055] The input timing generators 205 ₁-205 _(N) receive a phase andfrequency adjustment signal from the digital PMD 130, but may alsoreceive a fast modulation signal or other control signals as well. Thedigital PMD 130 may also provide control signals (e.g., phase, frequencyand fast modulation signals, etc.) to the timing generator module 205for time synchronization and modulation control. The fast modulationcontrol signal may be used to implement, for example, chirp waveforms,PPM waveforms, such as fast time scale PPM waveforms, etc.

[0056] The digital PMD 130 may also provide control signals to, forexample, the encoder 225, the waveform generator 230, and thetransmitter front end 126, the T/R switch 110, the receiver front end122, the correlators 220 ₁-220 _(N), etc., for controlling, for example,amplifier gains, signal waveforms, filter passbands and notch functions,alternative demodulation and detecting processes, user codes, spreadingcodes, cover codes, etc.

[0057] During signal acquisition, the digital PMD 130 adjusts the phaseinput of the first input timing generator 205 ₁, in an attempt for thefirst tracking correlator 220 ₁ to identify and the match the timing ofthe signal produced at the receiver with the timing of the arrivingsignal. When the received signal and the locally-generated signalcoincide in time with one another, the digital PMD 130 senses the highsignal strength or high SNR and begins to track, indicating that thereceiver is synchronized with the received signal.

[0058] Once synchronized, the receiver will operate in a track mode,where the first input timing generator 205 ₁ is adjusted by way of acontinuing series of phase adjustments to counteract any differences intiming of the first input timing generator 205 ₁ and the incomingsignal. However, a feature of the present invention is that by sensingthe mean of the phase adjustments over a known period of time, thedigital PMD 130 adjusts the frequency of the first input timinggenerator 205 ₁ so that the mean of the phase adjustments becomes zero.

[0059] The frequency is adjusted in this instance because it is clearfrom the pattern of phase adjustments that there is a frequency offsetbetween the first input timing generator 205 ₁ and the clocking of thereceived signal. Similar operations may be performed on the secondthrough Nth input timing generators 205 ₂-205 _(N), so that each fingerof the receiver can recover the signal delayed by different amounts,such as the delays caused by multipath (i.e., scattering along differentpaths via reflecting off of local objects).

[0060] A feature of the transceiver in FIG. 2 is that it includes aplurality of tracking correlators 220 ₁-220 _(N). By providing aplurality of correlators, several advantages are obtained. First, it ispossible to achieve synchronization more quickly (i.e., by operatingparallel sets of correlation arms to find strong SNR points overdifferent code-wheel segments). Second, during a receive mode ofoperation, the multiple arms can resolve and lock onto differentmultipath components of a signal. Through coherent addition, the UWBcommunication system uses the energy from the different multipath signalcomponents to reinforce the received signal, thereby improving signal tonoise ratio. Third, by providing a plurality of tracking correlatorarms, it is also possible to use one arm to continuously scan thechannel for a better signal than is being received on other arms.

[0061] In one embodiment of the present invention, if and when thescanning arm finds a multipath term with higher SNR than another armthat is being used to demodulate data, the role of the arms is switched(i.e., the arm with the higher SNR is used to demodulate data, while thearm with the lower SNR begins searching). In this way, thecommunications system dynamically adapts to changing channel conditions.

[0062] The digital PMD 130 receives the information from the differentcorrelators 220 ₁-220 _(N) and decodes the data. The digital PMD 130also provides control signals for controlling the receiver front end122, e.g., such as gain, filter selection, filter adaptation, etc., andadjusting the synchronization and tracking operations by way of thetiming generator module 205.

[0063] The digital PMD 130 is connected to the PLCP 140 (not shown inFIG. 2), which serves as an interface between the communication linkfeature of the present invention and other higher level applicationsthat will use the wireless UWB communication link for performing otherfunctions. Some of these functions would include, for example,performing range-finding operations, wireless telephony, file sharing,personal digital assistant (PDA) functions, embedded control functions,location-finding operations, etc.

[0064] On the transmit portion of the transceiver shown in FIG. 2, anoutput timing generator 205 ₀ also receives phase, frequency and/or fastmodulation adjustment signals for use in encoding a UWB waveform fromthe digital PMD 130. Data and user codes (via a control signal) areprovided to the encoder 225, which in the case of an embodiment of thepresent invention using time-modulation passes command signals (e.g.,Δt) to the output timing generator 205 ₀ for providing the time at whichto send a pulse. In this way, encoding of the data into the transmittedwaveform may be performed.

[0065] When the shape of the different pulses are modulated according tothe data and/or codes, the encoder 225 produces the command signals as away to select different shapes for generating particular waveforms inthe waveform generator 230. For example, the data may be grouped inmultiple data bits per channel symbol. The waveform generator 230 thenproduces the requested waveform at a particular time as indicated by thetiming generator 205 ₀. The output of the waveform generator is thenfiltered and amplified as needed in the transmitter front end 126 beforebeing transmitted from the antenna 105 by way of the T/R switch 110.

[0066] In another embodiment of the present invention, the transmitpower is set low enough that the transmitter and receiver are simplyalternately powered down without need for the T/R switch 110. Also, insome embodiments of the present invention no transmitter front end 126is needed because the desired power level and spectrum are directlyuseable from the waveform generator 230. In addition, the transmitterfront end 126 may be included in the waveform generator 230 depending onthe implementation of the present invention.

[0067] A feature of the UWB communications system disclosed, is that atransmitted waveform can be made to have a nearly continuous power flow,for example, by using a high chipping rate, where individual wavelets inthe waveform are placed nearly back-to-back. This configuration allowsthe system to operate at low peak voltages, yet produce ample averagetransmit power to operate effectively. As a result, sub-micron geometryCMOS switches, for example, running at one-volt levels, can be used todirectly drive the antenna 105 such that no separate amplification isrequired in the transmitter front end 126. In this way, the entire radiocan be integrated on a single monolithic integrated circuit.

[0068] Under certain operating conditions, the system can be operatedwithout any filters in the transmitter front end 126. If, however, thesystem is to be operated, for example, with another radio system, thetransmitter front end 126 can be used to provide a notch function tolimit interference with other radio systems. In this way, the system canoperate simultaneously with other radio systems, providing advantagesover conventional devices that use avalanching type devices connectedstraight to an antenna, such that it is difficult to include filterstherein.

[0069]FIG. 3 illustrates a processor system 300 according to a preferredembodiment of the present invention. In this embodiment, the processorsystem 300 includes a processor unit 301, a display 315, one or moreinput devices 317, a cursor control 319, a printer 321, a network link323, a communications network 325, a host computer 327, an InternetProtocol (IP) network 329, and a mobile device 331. The processor unit301 includes a bus 303, a processor 305, a main memory 307, a read onlymemory (ROM) 309, a storage device 311, and a communication interface313. Alternate embodiments may omit various elements.

[0070] The bus 303 operates to communicate information throughout theprocessor unit. It is preferably a data bus or other communicationmechanism for communicating information.

[0071] The processor 305 is coupled with the bus 303 and operates toprocess the information.

[0072] The main memory 307 may be a random access memory (RAM) or otherdynamic storage device (e.g., dynamic RAM (DRAM), static RAM (SRAM),synchronous DRAM (SDRAM), flash RAM). It is preferably coupled to thebus 303 for storing information and instructions to be executed by theprocessor 305. In addition, a main memory 307 may be used for storingtemporary variables or other intermediate information during executionof instructions to be executed by the processor 305.

[0073] The ROM 309 may be a simple read-only memory, or may be anotherkind of static storage device (e.g., programmable ROM (PROM), erasablePROM (EPROM), and electrically erasable PROM (EEPROM)). It is coupled tothe bus 303 and stores static information and instructions for theprocessor 305.

[0074] The storage device 311 may be a magnetic disk, an optical disc,or any other device suitable for storing data. It is provided andcoupled to the bus 303 and stores information and instructions.

[0075] The processor unit 301 may also include special purpose logicdevices (e.g., application specific integrated circuits (ASICs)) orconfigurable logic devices (e.g., simple programmable logic devices(SPLDs), complex programmable logic devices (CPLDs), or re-programmablefield programmable gate arrays (FPGAs)). Other removable media devices(e.g., a compact disc, a tape, and a removable magneto-optical media) orfixed, high density media drives may be added to the processor unit 301using an appropriate device bus (e.g., a small system interface (SCSI)bus, an enhanced integrated device electronics (IDE) bus, or anultra-direct memory access (DMA) bus). The processor unit 301 mayadditionally include a compact disc reader, a compact disc reader-writerunit, or a compact disc jukebox, each of which may be connected to thesame device bus or another device bus.

[0076] The processor system 301 may be coupled via the bus 303 to thedisplay 315. The display unit may be a cathode ray tube (CRT),,a liquidcrystal display (LCD), or any other suitable device for displayinginformation to a system user. A display or graphics card may control thedisplay 315.

[0077] The processor system 301 is also preferably connected to the oneor more input devices 317 and a cursor control 319 for communicatinginformation and command selections to the processor 305. The one or moreinput devices may include a keyboard, keypad, or other device fortransferring information and command selections. The cursor control 319may be a mouse, a trackball, cursor direction keys, or any suitabledevice for communicating direction information and command selections tothe processor 305 and for controlling cursor movement on the display315.

[0078] In addition, a printer 321 may provide printed listings of thedata structures or any other data stored and/or generated by theprocessor system 301.

[0079] The processor unit 301 performs a portion of all of theprocessing steps of the invention in response to the processor 305executing one or more sequences of one or more instructions contained ina memory, such as the main memory 307. Such instructions may be readinto the main memory 307 from another computer-readable medium, such asa storage device 311. One or more processors in a multi-processingarrangement may also be employed to execute the sequences ofinstructions contained in the main memory 307. In alternativeembodiments, hard-wired circuitry may be used in place of or incombination with software instructions. Thus, embodiments are notlimited to any specific combination of hardware circuitry and software.

[0080] As stated above, the processor unit 301 includes at least onecomputer readable medium or memory programmed according to the teachingsof the invention and for containing data structures, tables, records, orother data described herein. Stored on any one or on a combination ofcomputer readable media, the present invention includes software forcontrolling the system 301, for driving a device or devices forimplementing the invention, and for enabling the system 301 to interactwith a human user. Such software may include, but is not limited to,device drivers, operating systems, development tools, and applicationssoftware. Such computer readable media further includes the computerprogram product of the present invention for performing all or a portion(if processing is distributed) of the processing performed inimplementing the invention.

[0081] The computer code devices of the present invention may be anyinterpreted or executable code mechanism, including but not limited toscripts, interpretable programs, dynamic link libraries, Java or otherobject oriented classes, and complete executable programs. Moreover,parts of the processing of the present invention may be distributed forbetter performance, reliability, and/or cost.

[0082] The term “computer readable medium” as used herein refers to anymedium that participates in providing instructions to the processor 305for execution. A computer readable medium may take many forms, includingbut not limited to, non-volatile media, volatile media, and transmissionmedia. Non-volatile media includes, for example, optical, magneticdisks, and magneto-optical disks, such as the storage device 311.Volatile media includes dynamic memory, such as the main memory 307.Transmission media includes coaxial cables, copper wire and fiberoptics, including the wires that comprise the bus 303. Transmissionmedia may also take the form of acoustic or light waves, such as thosegenerated during radio wave and infrared data communications.

[0083] Common forms of computer readable media include, for example,hard disks, floppy disks, tape, magneto-optical disks, PROMs (EPROM,EEPROM, Flash EPROM), DRAM, SRAM, SDRAM, or any other magnetic medium,compact disks (e.g., CD-ROM), or any other optical medium, punch cards,paper tape, or other physical medium with patterns of holes, a carrierwave, carrierless transmissions, or any other medium from which a systemcan read.

[0084] Various forms of computer readable media may be involved inproviding one or more sequences of one or more instructions to theprocessor 305 for execution. For example, the instructions may initiallybe carried on a magnetic disk of a remote computer. The remote computercan load the instructions for implementing all or a portion of thepresent invention remotely into a dynamic memory and send theinstructions over a telephone line using a modem. A modem local tosystem 301 may receive the data on the telephone line and use aninfrared transmitter to convert the data to an infrared signal. Aninfrared detector coupled to the bus 303 can receive the data carried inthe infrared signal and place the data on the bus 303. The bus,303carries the data to the main memory 307, from which the processor 305retrieves and executes the instructions. The instructions received bythe main memory 307 may optionally be stored on a storage device 311either before or after execution by the processor 305.

[0085] The communications interface 313 provides a two-way UWB datacommunication coupling to a network link 323, which is connected to thecommunications network 325. The communications network 325 may be alocal area network (LAN), a personal area network (PAN), or the like.For example, the communication interface 313 may be a network interfacecard and the communications network may be a packet switched UWB-enabledPAN. As another example, the communication interface 313 may be a UWBaccessible asymmetrical digital subscriber line (ADSL) card, anintegrated services digital network (ISDN) card, or a modem to provide adata communication connection to a corresponding type of communicationsline.

[0086] The communications interface 313 may also include the hardware toprovide a two-way wireless communications coupling other than a UWBcoupling, or a hardwired coupling to the network link 323. Thus, thecommunications interface 313 may incorporate the UWB transceiver of FIG.1 or FIG. 8 as part of a universal interface that includes hardwired andnon-UWB wireless communications coupling to the network link 323.

[0087] The network link 323 typically provides data communicationthrough one or more networks to other data devices. For example, thenetwork link 323 may provide a connection through a LAN to the hostcomputer 327 or to data equipment operated by a service provider, whichprovides data communication services through the IP network 329.Moreover, the network link 323 may provide a connection through thecommunications network 325 to the mobile device 331, e.g., a personaldata assistant (PDA), laptop computer, or cellular telephone.

[0088] The communications network 325 and IP network 329 both preferablyuse electrical, electromagnetic, or optical signals that carry digitaldata streams. The signals through the various networks and the signalson the network link 323 and through the communication interface 313,which carry the digital data to and from the system 301, are exemplaryforms of carrier waves transporting the information. The processor unit301 can transmit notifications and receive data, including program code,through the communications network 325, the network link 323, and thecommunication interface 313.

[0089] The present invention uses the benefits offered by ultra wideband spread spectrum technology. From an energy spreading perspective,or from a resolution perspective, bandwidth and center frequency can betreated independently. The name UWB, however, was coined by a DARPAstudy panel and though the term “relative bandwidth” does not appear inthe name, a definition of UWB demands use of this term.

[0090] As recognized by the present inventors, the motivations forpreferring definitions based on bandwidth relative to center frequencyfollow from three primary desirable features. The first is immunity toscintillation and multipath fading. The only way to preventscintillation, speckle, and multipath fading is to have resolution thatis approximately equal to the wavelength. The second is penetratingmaterials with high bandwidth signals.

[0091] To communicate at the highest data rates through lossy media(i.e., media subject to high losses), or to do the highest resolutionradar imaging through or within lossy media, requires both lowfrequencies (to penetrate) and wide bandwidths (to resolve), which whentaken together require wide relative bandwidth. In this case, losses athigher frequencies are so great that these higher frequencies cannot beused. The definition of UWB is based on relative bandwidth because thesebenefits derive specifically from wide relative bandwidth and cannot beobtained with narrowband systems. A more complete discussion of thebenefits of UWB communications signals can be found in application Ser.No. 09/078,616 referenced above and incorporated herein by reference.

[0092] If B is the bandwidth, f_(c) is the center frequency, and f_(h)and f_(l) are the high and low frequency cutoffs (e.g. −6 dB from peak),then the fractional bandwidth, B_(f), is defined as $\begin{matrix}{B_{f} = {\frac{B}{f_{c}} = {\frac{\left( {f_{h} - f_{l}} \right)}{\left( {f_{h} + f_{l}} \right)/2}\quad.}}} & (1)\end{matrix}$

[0093] A UWB system is one that has a fractional bandwidth, B_(f), inthe range of 0.25 to 2.0, which means that a UWB system approximatelymatches its bandwidth to its center frequency. Said another way, thismeans that a UWB system matches resolution to wavelength.

[0094] The present invention provides a system and method that enablesdevice functions based on distance information. More specifically, thepresent invention allows a simplified method for enabling communicationsbetween a local wireless device and a remote wireless device based onthe distance between the wireless devices. In order to provide such adistance-based system that is practically usable, the wireless devicesinvolved must be able to discriminate distances at fine intervals; orstated another way, the wireless device must have accurate rangeresolution.

[0095] The present inventors have recognized that the range resolutionof a receiver is roughly inverse to the bandwidth of the transmitsignal. Therefore, narrowband systems having a bandwidth of 1 MHZ, suchas the Bluetooth technology previously discussed, have a rangeresolution of $\begin{matrix}{R_{res} = {\frac{c}{BW} = {\frac{3 \times 10^{8}\quad m\text{/}\sec}{1\quad {MHz}} = {300\quad m}}}} & (2)\end{matrix}$

[0096] Therefore, a device implementing Bluetooth protocol even ifconfigured to determine distance, can discriminate between remotedevices based on distance only if the devices are 300 meters apart.Similarly, wireless devices based on IEEE 802.11 A and B standards havea bandwidth of 20 MHZ and a range resolution of 15 meters orapproximately 45 feet. This resolution does not provide the ability todiscriminate between remote devices using distance information that isneeded for short range exchanges that are typical of wireless hand helddevices such as the exchange of electronic business cards.

[0097] The present inventors have recognized that using an ultra wideband system, range resolutions can be accomplished that have practicalsignificance in distinguishing between remote wireless devices. Forexample, an ultra wide bandwidth system having 3 GHz of bandwidth has arange resolution of 0.1 meters. Even greater bandwidth systems canaccomplish resolutions on the order of centimeters. Thus, as realized bythe present inventors, a local UWB device can compute a unique distanceto remote UWB devices as long as the actual distance from the localdevice to each remote device differs on the order of centimeters, whichis a common scenario for current uses of wireless devices such as PDAs.

[0098]FIG. 4 discloses a wireless network 400 in which a plurality ofwireless devices may exchange information. The wireless network 400 maybe WPAN, WLAN, or some other wireless network in which wireless devicesmake point-to-point connections, or point-to-multipoint connections onthe shared channel of a piconet. The wireless network 400 includes alocal device 405 and first through N^(th) remote devices 410 ₁-410 _(N).

[0099] The local device 405 is linked to the first through N^(th) remotedevices 410 ₁-41o_(N) via UWB links 415 ₁-415 _(N), respectively. TheUWB links are preferably full duplex communications links that carrydata, voice, video, or any other analog or digital information inaccordance with the present invention. However, simplex communicationsin either direction may be used in alternate embodiments.

[0100] Each of the wireless devices 405 and 410 ₁ through 410 _(N) maybe a mobile device such as a mobile telephone, a laptop computer orpersonal digital assistant (PDA), or a fixed structure device such as aretail store kiosk or some other fixed structure device for deliveringinformation to other wireless devices. It is to be understood thatdevice 405 is referred to as a “local device” and devices 410 ₁ through410 _(N) are referred to as “remote devices” for purposes of descriptiononly, and that the present invention is not limited to an infrastructuresystem having an access point and may be implemented in an ad hoc systemwherein any device in the network can act as a master and/or a slavedevice and no access point is needed.

[0101] Each of the of the devices 405 and 410 ₂ through 410 _(N)includes a processor system, such as the one described in FIG. 3, forinputting, storing, and processing data in accordance with the presentinvention. Therefore, local device 405 and each remote device 410 ₁through 410 _(N) also includes a UWB transceiver, such as thetransceiver described in FIGS. 1 and 2, that transmits and receives aUWB signal 420 via a UWB antenna such as the antennas 105 described inFIGS. 1 and 2.

[0102] The UWB antenna 105 is preferably an antenna as described in thepatent application entitled ELECTRICALLY SMALL PLANAR UWB ANTENNA(Attorney Docket 10188-0005-8), or application Ser. No. 09/563,292,filed May 3, 2000 entitled PLANAR UWB ANTENNA WITH INTEGRATEDTRANSMITTER AND RECEIVER CIRCUITS (Attorney Docket 10188-0006-8)referenced above and incorporated herein by reference, but may be anyknown UWB antenna. The UWB signal 420 includes data for communicatingwith remote devices based on distance in accordance with the presentinvention.

[0103]FIG. 5 is a general flow chart that describes a process forenabling device functions based on distance information in accordancewith the present invention. The process starts when a device is turnedon or enters the listening range of other wireless devices communicatingon a wireless network. In step 501, the local device 405 establishes alink with each remote device 410 ₁ through 410 _(N) using a multipleaccess protocol. Examples of multiple access protocols may be found inthe IEEE 802.11 standard, final draft approved Jun. 26, 1997, and theBluetooth specification “Specification of the Bluetooth System”, V.1.OB,Dec. 1, 1999, core specification—Vol. 1, the entire contents of whichare incorporated herein by reference.

[0104] It is to be understood that the features and benefits of thepresent invention do not depend on a particular multiple access protocoland any of the above named protocols or any other multiple accessprotocol may be used to practice the present invention as will beunderstood to one of ordinary skill in the art. However, in a preferredembodiment, the multiple access protocol provides the capability for thelocal device 405 to establish unique and independent UWB links 415 ₁,415 ₂, . . . , 415 _(N) with remote devices 410 ₁, 410 ₂, . . . , 410_(N) respectively as will be discussed with respect to the exemplaryprotocol of FIG. 6.

[0105] After unique links 415 ₁, 415 ₂, . . . , 415 _(N) areestablished, the local device 405 determines a distance to each linkedremote device as shown in step 503. In determining the distance, localdevice 405 exchanges data with remote devices 410 ₁, 410 ₂, . . . 410_(N) via their respective unique links. Each distance determined by thelocal device 405 is associated with the unique link on which thedistance determining information was exchanged in order to associate adetermined distance with a remote device as will be discussed below withreference to FIG. 7.

[0106] Once the distance to each remote device is determined, the localdevice 405 then enables communications with each remote device in step505 based on the distances determined in step 503. Due to the rangeresolution of the UWB system included in each of the devices of FIG. 4,the distance determined may be accurate on the order of centimeters, asdiscussed above. Therefore the probability of having remote devices atequal distances is very low and the local device 405 can differentiatebetween remote devices 410 ₁, 410 ₂, . . . , 410 _(N) based on thedistance determined for each device. For example, the local device mayautomatically enable data communications with devices that are within apredefined range at any given time while all remote devices outside thepredefined range will be blocked from data communications with the localdevice as will be described below with respect to FIG. 8.

[0107] Alternatively, the local device may enable data communicationswith devices, that enter a predefined authentication range and maintaindata communications with such devices until the user of the local devicedecides to terminate data communications with an authenticated remotedevice as will be described below with respect to FIG. 10.

[0108] Or a local device may display a positional map of all users inrelation to the local device so that the user of the local device mayselect those remote devices that the user wants to communicate with aswill be discussed below with respect to FIGS. 11 and 12.

[0109] It is to be understood that while the above examples discussenabling and blocking data communications based on distance to remotedevice, advantages of the present invention may be obtained when anyfunction of the local device 405 is performed using the distanceinformation obtained in step 503. For example, the local device 405 maystore data sent from remote devices within a predefined range while onlydisplaying the information sent from remote devices outside that range.As another example, the local device 405 may notify the device user orautomatically enter a sleep mode if no remote devices are within apredefined range. These or any other internal functions of the localdevice 405 may be accomplished based on distance information obtained inaccordance with the present invention.

[0110] According to a preferred embodiment, in addition to determiningthe distance to remote devices 410 ₁ through 410 _(N) and enablingcommunications based on the distance determined, the local device 405updates distance information by way of a loop 507. The loop 507 returnsto step 503 (determining distance for the remote devices) and may beperformed only on devices that have been blocked from communicating withthe local device 405, or on both enabled and blocked remote devices.

[0111] In step 509, the local device 405 periodically updates its linksto the remote devices 410 ₁ through 410 _(N). In doing so, another loop511 is established, which returns to step 501 (establishing a uniquelink with remote devices). In executing loop 511, the local device 405determines if remote devices that were previously linked to are nolonger available, and whether new devices have entered the listeningrange of the local device 405. Unique communications links are thendestroyed or created in step 509 depending on the information obtainedby executing the loop 511.

[0112] The process of enabling device functions and/or communicatingwith remote wireless devices ends when power to the local device 405 isturned off or the local device is outside the communicating area of theremote devices 410 ₁ through 410 _(N). While “end” is shown asproceeding from step 509 in FIG. 5, it is to be understood that the endmay occur at any point in the process of FIG. 5.

[0113]FIG. 6 is a flow chart describing the process whereby the localdevice 405 establishes unique communication links 415 ₁, 415 ₂, . . . ,415 _(N) with remote devices 410 ₁, 410 ₂, . . . , 410 _(N),respectively by using an exemplary multiple access protocol inaccordance with the present invention. In step 601, the local device 405transmits a join message to all unlinked remote devices within a rangeof the transmission power of the local device 405. The join message maybe a simple UWB signal that enables unlinked remote devices tosynchronize to the local device 405, or may include information such asa device identifier, a device type identifier, a standard bit code,and/or any other information desired to be transmitted from local device405 to the unlinked remote devices 410 ₁ through 410 _(N). According toa preferred embodiment, the join message is transmitted only to unlinkedremote devices and not over the unique links of synchronized remotedevices, so that the local device 405 may form unique links with newremote devices entering step 601 (as indicated by loop 511) in FIG. 6.

[0114] In step 603, each remote device that is listening then receivesthe join message and synchronizes with the local device 405. In step603, each of the remote devices 410 ₁ through 410 _(N) aligns in time aparticular pulse sequence produced in the remote device with the pulsesequence of the joint signal sent from the local device. Thissynchronization of the remote devices 410 ₁ through 410 _(N) ispreferably performed in accordance with the process described in any oneof the following patent applications: Ser. No. 09/685,195, for“ULTRAWIDE BANDWIDTH SYSTEM AND METHOD FOR FAST SYNCHRONIZATION,” filedOct. 10, 2000, Ser. No. 09/684,401, for “ULTRA WIDE BANDWIDTH SYSTEM ANDMETHOD FOR FAST SYNCHRONIZATION USING SUB CODE SPINS,” filed Oct. 10,2000; and Ser. No. 09/685,196, for “ULTRA WIDE BANDWIDTH SYSTEM ANDMETHOD FOR FAST SYNCHRONIZATION USING MULTIPLE DETECTION ARMS, filedOct. 10, 2000, which are incorporated by reference in their entirely.However, synchronization may take place by any known method ofsynchronizing wireless devices.

[0115] Once the remote devices 410 ₁ through 410 _(N) are synchronizedwith the transmitted signal of the local device 405, each remote devicetransmits a reply to the join signal as shown in step 605. Each reply isa UWB signal that includes a unique identifier associated with theremote device from which the reply is transmitted. The unique identifiermay be a device address stored in ROM 309 (see FIG. 3), for example, ora unique delay time for the remote device as will be described below.Thus, in step 605, each of the remote devices 410 ₁ through 410 _(N)encodes its unique identifier information and attaches the informationto a reply signal to be transmitted back to the local device 405. Instep 607, the local device 405 receives each reply and synchronizes witheach remote device that sent a reply.

[0116] In step 609, the local device 405 decodes each unique identifierand establishes unique communications links 415 ₁, 415 ₂, . . . , 415_(N) with remote devices 410 ₁, 410 ₂, . . . , 410 _(N), respectively.In establishing the unique communications links, the local device 405associates the unique identifier of each remote device with acommunications link established by the synchronization process for theparticular remote device. The unique identifier and associated links arethen stored to the main memory 307 (See FIG. 3) of the local device 405for use in determining distance as will be described below.

[0117] Each unique link 415 ₁, 415 ₂, . . . , 415 _(N) is preferably alow-level communications link that is allocated a minimal amount ofbandwidth available to the local device 405. The amount of bandwidthallocated may vary but is preferably an amount that is sufficient forthe local device 405 to maintain awareness of the presence of the remotedevices 410 ₁ through 410 _(N) and to determine distance to each remotedevice.

[0118]FIG. 7 describes a process of determining distance to each linkedremote device in accordance with an embodiment of the present invention.In step 701, a distance-determining message is generated in the localdevice 405 and transmitted to each linked remote device 410 ₁, 410 ₂, .. . , 410 _(N) via the unique communication links 415 ₁, 415 ₂, . . . ,415 _(N). In an initial situation where the local device 405 has notenabled communications with any of the remote devices 410 ₁ through 410_(N) either because no distance information is known or because allremote devices have been blocked, the distance determining message is asimple UWB signal the acts as a notification and/or request to eachremote device that a distance determination is being made by the localdevice 405.

[0119] Alternatively, where the local device 405 knows distanceinformation for the remote devices and has enabled communications forcertain remote devices, the distance determining message may be attachedto a communication for a particular link as indicated by input 507 andas will be described with respect to FIG. 8.

[0120] For each distance determining message sent on each uniquecommunications link 410 ₁ through 410 _(N), the local device 405 marks atime t₁ as the transmitting time that the message was sent out for theparticular communications link as shown in step 703. Transmit time t₁ isobtained by a system clock in the processor system 301 of the localdevice 405. Each transmit time t₁ is associated with one of the uniqueidentifiers stored in step 609 based on the unique link over which thedistance determining massage was transmitted. The transmit times andassociated identifiers are then stored in the main memory 307 of localdevice 405 so that the transmit times may be retrieved to determine thedistance to each remote device.

[0121] In step 705, the linked remote devices 410 ₁, 410 ₂, . . . , 410_(N) receive the distance-determining message via a respective uniquelink and transmit a response to the local device 405 over the sameunique link. As with the distance-determining message transmitted instep 701, the response message from the remote devices may include acommunication if the link responded on is an enabled link.

[0122] In step 707, the local device 405 receives responses sent fromthe linked remote devices via respective unique links and marks areceive time t₂ for each response received as seen in step 709. As withthe transmit times t₁, each receive time t₂ is associated with theunique identifier of a respective link and stored in main memory 307 foruse in calculating a distance from the local device 405 to each remotedevice 410 ₁ through 410 _(N).

[0123] Before computing a distance to each linked remote device, thelocal device 405 first determines a processing delay d for each linkedremote device as seen in step 711. The processing delay d is the timedelay between the remote device receiving the distance determiningmessage and transmitting a response and includes at least the amount oftime necessary for the remote device to process the distance determiningmessage and form a response.

[0124] According to one embodiment, the processing delay d is determinedby retrieving the delay from the memory of the local device 405. In thisembodiment, the local device 405 receives information from each remotedevice about the radio type of the remote device, as part of the replyand/or response received from the remote devices as discussed withrespect to steps 607 and 707 respectively. Alternatively, the typeinformation may be received as part of an independent signal sent by theremote devices. With the remote device type known, the local device 405then refers to a look up table (LUT) stored in memory 307 or ROM 309(See FIG. 3) to determine a predefined processing delay for the radiotype.

[0125] In an alternative embodiment, the processing delay d of eachremote device 410 ₁ through 410 _(N) may be transmitted to the localdevice 405 as part of the reply, the response, or some independentsignal. In this embodiment, the processing delay d may be the inherentdelay of the remote device plus some arbitrary delay time that gives theremote device a unique delay time the may be used as the uniqueidentifier for the remote device as discussed with respect to step 605of FIG. 6 above. The processing delay d is then stored in main memory307 for use in establishing unique communications links with remotedevices and in determining the distance to remote devices.

[0126] In step 713, the local device 405 calculates the round trip timeT_(rt) for each linked remote device 410 ₁ through 410 _(N). In thisstep, the,local device 405 retrieves the transmitting time t₁, receivingtime t₂, and processing delay time d of a particular unique link to aremote device from main memory 307 and ROM 309 as discussed above. Theprocessor 305 of the local device 405 then computes the total round triptime according to the following formula:

T _(rt) =t ₂ −t ₁ −d   (3)

[0127] Thus, the round trip time is the time that the distancedetermining signal and the response signal travel through the wirelessmedium and is different for each remote device. Each round trip timeT_(rt) is stored to main memory 307 where the processor 305 of the localdevice 405 retrieves values for T_(rt) and computes the distance D toeach remote device according to the following formula: $\begin{matrix}{D = {c \cdot \frac{T_{rt}}{2}}} & (4)\end{matrix}$

[0128] where c is the speed of light (i.e., the speed at which an RFsignal travels through the wireless medium). The distance D for eachremote device 410 ₁ through 410 _(N) is then associated with the uniqueidentifier of the unique communications link over which the distance wasdetermined and is stored in main memory 307 so that systems software ofthe local device 405 may retrieve the distance information to enable orblock communications with the remote devices based on their distancefrom the local device 405.

[0129]FIG. 8 is a flow chart describing the process of automaticallyenabling or blocking communications with each linked remote device 410 ₁through 410 _(N) based on the distance determined in accordance with anembodiment of the present invention.

[0130] In step 801, the local device 405 obtains a range criteria rinput to the local device. The range criteria r is a predefined distancethat serves as a benchmark for enabling communications features of thelocal device 405 based on distance information. The range criteria r ispreferably programmable by the user in which case the user inputs therange criteria into the main memory 307 of the local device 405 via theinput device 315 for example, but may be set by the manufacturer of thelocal device in which case the range criteria is stored in the ROM 309of the local device 405.

[0131] In step 803, the range criteria r is compared with the distance Ddetermined for each remote device and stored in main memory 307 asdiscussed with respect to step 715 above. In making this comparison, theprocessor 305 determines whether the distance D for a particular remotedevice is less than, equal, or greater than the range criteria r.

[0132] If the results of the comparison indicate that the distance tothe particular remote device is greater that the range criteria (i.e.,D>r), the local device determines that the remote device is out of rangeand, according to the embodiment of FIG. 8, blocks communications withthe out of range remote device as shown in step 805.

[0133] On the other hand, if the results of the comparison indicate thatthe distance to a particular remote device is less than or equal to therange criteria (i.e., D≦r), according to the embodiment of FIG. 8,communications are enabled with the in range remote device as shown instep 809.

[0134] For example, if the range criteria of the local device 405 is setto be 3 feet, and the distance from the local device 405 to the remotedevices 410 ₁, 410 ₂, and, 410 _(N) is 2 feet, 3 feet, and 8 feet,respectively, then the local device 405 enables communications overlinks 415 ₁ and 415 ₂ and blocks data communications over link 415 _(N).A communication is data, voice, video, or any other analog or digitalinformation sent or received by the user of the local device 405 to orfrom remote device in accordance with the present invention.

[0135] According to one embodiment of the present invention,communications are blocked and enabled at the applications softwarelevel of the local device 405. That is, communications transmitted toremote devices are prevented from being sent to the out of range remotedevices (410 _(N) in the above example) by the application softwaresending a command message to the MAC layer of the local device 405indicating that a particular message should be transmitted on links 415₁ and 415 ₂, but not on links 415 _(N). In receiving communications, theapplications software displays the communications received on links 415₁ and 415 ₂ to the user, but does not display the communicationsreceived on links 415 _(N).

[0136] In a preferred embodiment, however, communications to and fromthe out of range remote device 400 _(N) may be blocked at the MAC layerin the stack of the local device 405. In this embodiment, the localdevice 405 allocates a minimal amount of available bandwidth to the link415 _(N) associated with the out-of-range device 400 _(N), and arelatively large amount of bandwidth to enabled links associated within-range remote devices 410 ₁ and 410 ₂. In other words, a communicationsent to remote devices 410 ₁ and 410 ₂ via links 415 ₁ and 415 ₂ willnot be sent on the blocked communications link. And a communicationreceived from the out-of-range remote device 410 _(N) will not bedecoded and processed by the local device 405. In this embodiment, thereceived communications from out of range devices is never processed andpropagated up the stack of the local device 405 resulting in a moreefficient system.

[0137] According to the preferred embodiment, the minimal bandwidthallocated to each of the out of range device 410 _(N) is sufficient toupdate the distance information so that the local device 405 cancontinue monitoring the distance of the out of range remote device 410_(N) as seen in step 807. In updating the distance information, a newdistance-determining signal is sent to the blocked remote device 410_(N) via link 415 _(N) in accordance with the loop 507 as discussed inFIGS. 5 and 7. Therefore, the distance from the local device 405 to theout of range remote device 410 _(N) is again determined by transmittinga distance determining signal in accordance with the process of FIG. 7.

[0138] Because the remote device 410 _(N) is out of range, however, nocommunications are attached to the distance determining signal asindicated in FIG. 8. If on the next distance determining message thedistance to the remote device 410 _(N) has changed due to movement ofthe remote device 410 _(N) or the local device 405, then the localdevice 405 enables communications with the remote device 410 _(N), ifthe new distances are less than or equal to the range criteria as seenin step 809. This operation is performed as necessary for each of theremote devices 410 ₁, 410 ₂, . . . , 410 _(N) that are out of range.

[0139] In enabling communications in step 809, the local device 405allocates a large amount of the available bandwidth to thecommunications links 415 ₁ and 415 ₂ associated with the remote devices410 ₁ and 410 ₂ so that communications can be transmitted or receivedover these links as discussed above. In addition to transmitting andreceiving communications on the enabled links, the local device alsoupdates distance information for the enabled remote devices 410 ₁ and410 ₂ as shown in step 811.

[0140] In updating the distance information, a new distance-determiningsignal is sent to the enabled remote devices 410 ₁ and 410 ₂ via links415 ₁ and 415 ₂, respectively in accordance with the loop 507.Therefore, the distance from the local device 405 to the in range remotedevices 410 ₁ and 410 ₂ is again determined by transmitting a distancedetermining signal in accordance with the process of FIG. 7.

[0141] Because the remote devices 410 ₁ and 410 ₂ are within the rangecriteria, communications may be attached to the distance-determiningsignal as indicated in FIG. 8. If on the next distance determiningmessage the distance to the remote devices 410 ₁ and 410 ₂ have becomegreater than the range criteria, then the remote devices are determinedto now be out of range and the local device 405 blocks communications asseen in step 805.

[0142] Along with the process of updating of distance information forenabled and blocked links of remote devices, the local device 405continually updates link information as shown by connector C in FIG. 8.In a preferred embodiment of the present invention, the local device 405may be programmed to only allow a limited number of remote devices tolink up with the local device 405. As the bandwidth of the local device405 is fixed, limitation of linked device prevents a slowdown ofcommunications to enabled devices. Therefore, the local device 405 keepsa network count of the remote devices that are linked with the localdevice 405. FIG. 9 describes the process for updating the communicationslinks of the network 400 based on the network count in accordance withthe present invention.

[0143] In step 901, the local device 405 determines whether any ofremote devices 410 ₁, 410 ₂, . . . , 410 _(N) have exited the network400 due to the user of the device turning off power to the remotedevice, or exiting the area in which the remote device can receive thetransmit power of the local device and/or exiting the area in which thelocal device can receive the transmit power of the remote device. Thisdetermination may be made based on synchronization information with theremote devices or based on an exit signal transmitted from the remotedevice to the local device 405. In step 903, the local device 405,updates a count of remote devices on the wireless network 400 based onthe determination made in step 901. If no linked remote devices haveexited the network, the count remains the same, and the network count isdecremented for each remote device that has left the network.

[0144] In step 905, the local device 405 determines if a new remotedevice has attempted to enter the network 400. This determination ismade based on the unique identifiers received in the replies obtainedfrom remote devices as discussed in FIG. 6. If a new unique identifieris found that is not linked with the local device 405, the local devicedetermines if the network count is at maximum capacity as seen bydecision block 907. If the network count is at maximum capacity, thelocal device 405 returns to step 901 of determining whether a remotedevice has exited the network 400 as seen by loop 909. Local device 405continues in loop 909 without sending a new join message to unlinkeddevices until the network count is less than the maximum capacity atwhich time the local device will increment the network counter inaccordance with the number of new remote devices that have attempted toenter the network as seen in step, 911. After adding the new remotedevices to the network counter, the local device executes loop 511whereby a new join code is sent out to remote devices so that new remotedevices may be able to join the network 400 as discussed in FIG. 5.

[0145] Thus, according to the embodiment of the present invention shownin FIGS. 6-9, the local device 405 automatically enables and blocks datacommunications with remote devices 410 ₁, 410 ₂, . . . , 410 _(N) basedon the distance to each remote device 410 ₁, 410 ₂, . . . , 410 _(N). Asthe local device continually updates distance information for all linkeddevices while also searching for new remote devices to join the network,the network established according to this embodiment is a dynamicnetwork in which communications with remote devices may be enabled withthe local device 405 based on their distance to the local device 405without the need for the user of the local device 405 to select fromamong a list of remote devices 410 ₁, 410 ₂, . . . , 410 _(N) asdiscussed in the background section above.

[0146] The alternative embodiment of the present invention disclosed inFIG. 10 describes a process for authenticating communications withlinked remote devices based on distance information. In step 1001, thelocal device 405 obtains an authentication range a of the local device.As with the range criteria r discussed above, the authentication range ais preferably programmable by the user in which case the user inputs theauthentication range into the main memory 307 of the local device 405via the input device 315 for example, but may be set by the manufacturerof the device in which case the authentication range, is stored in theROM 309 of the local device 405. According to the embodiment of FIG. 10however, the authentication range a serves to enable, or authenticate,communications with remote devices 410 ₁, 410 ₂, . . . , 410 _(N)regardless of the distance of the authenticated remote device thereafteras will be described below.

[0147] In step 1003, the authentication range a is compared with thedistance D determined for each remote device 410 ₁, 410 ₂, . . . , 410_(N) and stored in main memory 307 as discussed with respect to step 715above. In making this comparison, the processor 305 determines whetherthe distance D for a particular remote device 410 ₁, 410 ₂, . . . , or410 _(N) is less than, equal, or greater than the authentication rangea.

[0148] In decision block 1005, the local device 405 determines whetherto authenticate remote devices 410 ₁, 410 ₂, . . . , 410 _(N) based onthe comparison made in step 1003 of FIG. 10. If the results of thecomparison indicate that the distance to the particular remote device410 ₁, 410 ₂, . . . , or 410 _(N) is greater that the authenticationrange (i.e., D>a), the local device determines that the remote device410 ₁, 410 ₂, . . . , or 410 _(N) cannot be authenticated and, accordingto the embodiment of FIG. 10, blocks communications with thenon-authenticated remote device 410 ₁, 410 ₂, . . . , or 410 _(N) asshown in step 1007.

[0149] On the other hand, if the results of the comparison indicate thatthe distance to a particular remote device 410 ₁, 410 ₂, . . . , or 410_(N) is less than or equal to the authentication range (i.e., D≦a),according to the embodiment of FIG. 10, communications are enabled withthe authenticated remote device as shown in step 1011. For example, ifthe authentication range a of the local device 405 is set to be 1 foot,and at any time the first remote device 410 ₁ enters within thatdistance to the local device 405, communications with first remotedevice 410 ₁ will be enabled regardless of the distance of the firstremote device 410 ₁ thereafter. Similarly, if the second remote device410 ₂ never enters within 1 foot of the local device 405, the link 415 ₂associated with the second remote device 410 ₂ will never get enabled.

[0150] As with the embodiment of FIG. 8, the local device 405 updatesdistance information for non-authenticated remote devices in step 1009,and if the non-authenticated device, for example the second remotedevice 410 ₂ as indicated above, enters the authentication range of thelocal device 405, then the device is authenticated and the secondcommunications link 415 ₂ associated with the second remote device 410 ₂is enabled for transmitting and receiving communications.

[0151] Unlike the embodiment of FIG. 8, however, according to theembodiment of FIG. 10, distance information is not updated forauthenticated devices as indicated by the connection C in FIG. 10.Rather, once a remote device 410 ₁, 410 ₂, . . . , or 410 _(N) isauthenticated by entering within the authentication range of the localdevice 405, then the remote device 410 ₁, 410 ₂, . . . , or 410 _(N) isenabled regardless of the distance from the local device 405. Thus inthe example discussed above, no distance information will be updated forthe authenticated first remote device 410 ₁ until the user decides toterminate the authentication of the first remote device 410 ₁. Thisallows a greater amount of bandwidth to be used for communications toauthenticated remote devices 410 ₁, 410 ₂, . . . , 410 _(N).

[0152] Thus, according to the embodiment of the present invention shownin FIGS. 6, 7, 9, and 10, the local remote device 405 authenticatescommunications based on the distance to each remote device 410 ₁, 410 ₂,. . . , 410 _(N). As the local device 405 enables communications with aremote device that enters an authentication range of the local device405 and continually updates distance information for allnon-authenticated remote devices 410 ₁, 410 ₂, . . . , 410 _(N) whilealso searching for new remote devices 410 ₁, 410 ₂, . . . , 410 _(N) tojoin the network, the network established according to this embodimentis a dynamic network in which communications with remote devices 410 ₁,410 ₂, . . . , 410 _(N) may be enabled with the local device 405 basedon their distance to the local device 405 without the need for the userof the local device 405 to select from among a list of remote devices410 ₁, 410 ₂, . . . , 410 _(N) as discussed in the background sectionabove.

[0153] According to yet another embodiment of the present invention,distance information is used to provide a positional map of remotedevices 410 ₁, 410 ₂, . . . , 410 _(N) from which the user of the localdevice 405 can select the remote devices 410 ₁, 410 ₂, . . . , 410 _(N)for which communications links will be enabled. FIG. 11 shows a typicalconference room 1100 located adjacent to rooms 1200 and 1300. Theconference room 1100 has ten mobile wireless devices each of which isrepresented by an “X”, and four fixed reference devices represented byan “R”. A local mobile device within conference room 1100 is representedas a bold faced X 1001 while all remote mobile devices within conferenceroom 1100 are represented as a non-bolded X and mobile devices withinadjacent rooms 1200 and 1300 are represented by a “Y”. The referencedevices R₁, R₂, R₃, and R₄ are in fixed positions to provide a knownreference point from which the position of each mobile device X and Y ismeasured. The reference devices may be fixed structure devices or mobiledevices that remain stationary in conference room 1100 duringconferences.

[0154] As with the network of FIG. 4, while device 1101 is referred toas a “local device” and all other devices of FIG. 11 are referred to as“remote devices”, this nomenclature is for purposes of description onlyand it is to be understood that the embodiment shown in FIG. 11 is notlimited to an access point system and may be implemented in an ad hocsystem wherein any device in the network can act as a master and/or aslave device. Also as with the devices of FIG. 4, local device 1101 andeach remote device X, Y and R preferably includes a processor system,such as the one described in FIG. 3, for inputting, storing, andprocessing data in accordance with the present invention and a UWBtransceiver that transmits and receives a UWB signal which includes datafor communicating with remote devices based on distance in accordancewith the present invention.

[0155] Additionally, each wireless device shown in FIG. 11 preferablyincludes some sort of a compass for orienting the display 313 of thelocal device 1101. In this regard, the reference devices R₁, R₂, R₃, andR₄ are preferably located due north, south east and west and west of acenter point of the conference room 1100, as seen by the directionalarrows of FIG. 11, so that the display 313 of the local device 1101 canbe oriented in accordance with the direction in which the user of thelocal device is facing as will be discussed.

[0156] According to the embodiment related to FIG. 11, and withreference to FIG. 3, the display 313 of the processor system 301 oflocal device 1101 displays a graphical map of the position of eachremote device in conference room 1100 from which the user of the localdevice may choose remote devices to enable communications with. Thus thedisplay 313 appears as a top view of the conference room 1100 with eachdevice physically located in the conference room having a correspondingposition on the display 313 of the local device 1101. In making aselection, the user of local device 1101 looks at the display 313 andassociates the devices on the display with remote device users visuallyverified by the local user.

[0157] In a preferred embodiment, the reference marker that the localuser is facing always appears at the top of the display 313 so that thelocal user can easily associate the physical location of a device withthe corresponding screen location.

[0158]FIG. 12 shows a process for enabling and disabling communicationwith remote devices based on selections made on a positional mapobtained from distance information in accordance with the presentinvention. In this embodiment, the local device 1101 establishes aunique link with each remote device, including mobile devices X,reference devices R₁-R₄, and mobile devices Y as described in FIG. 6,and determines distance to each remote device as described in FIG. 7.

[0159] In step 1201, the local device 1101 transmits aposition-determining message to all linked remote devices X, R, and Yvia the unique links established with each device. Theposition-determining message may be a simple UWB signal that indicatesthat the local device 1101 is requesting the data necessary to determineposition information from each linked remote device. Alternatively, aswith the distance determining message discussed above, the positiondetermining message may be included in a communication to devicespreviously enabled by the local device 1101.

[0160] In step 1203, each of the linked remote devices receives theposition-determining message and transmits an answer to the local device1101 via a respective communication link. In this step, each of thelinked remote devices encodes position information obtained by theremote device and includes the position information in the answertransmitted. The position information includes the distance from theanswering remote device to each other remote device X, R, and Y. Forexample, referring to FIG. 11, mobile device 1103 will have acontinually updated database of the distance from itself to referencedevice R₁, to reference device R₃, to device 1105, and each other deviceas indicated by dashed lines D₁-D₄ of FIG. 11. Similarly, device 1105will have a continually updated database of the distance from itself toeach other device as shown by dashed lines D_(a)-D_(c) of FIG. 11.

[0161] In step 1203 of FIG. 12, devices 1103 and 1105 encode thisposition information and transmit it as part of the answer to localdevice 1101. According to a preferred embodiment, the positioninformation may include distance from the answering remote device to alimited number of remote devices when the number of remote devices inthe listening range of the local device 1101 is large. Moreover, remotedevices may cooperate with one another to ensure that duplicate distanceinformation (such as distance D₃ and D_(b)) is not transmitted to localdevice 1101 more than once. These features reduce the amount of data tobe processed by processor 305 of the local device 1101 and thereforeincreases the speed at which the local device 1101 can displaypositional updates on the display 313.

[0162] In addition to this positional information, the answer of thereference devices R₁ through R₄ includes data identifying the referencedevice as a reference device as well as the unique position of thereference device. For example, reference device R₁ of FIG. 11 wouldencode data indicating that the position of R₁ is on the north wall ofthe conference room 1100. According to one embodiment, this informationis input into the reference devices R₁-R₄ by a user when the conferenceroom 1100 is set up for positional capabilities. This data allows aparticular reference device to be placed at the top of the display 313when a compass of the local device indicates that the local user isfacing the reference device as will be discussed.

[0163] In step 1205, the local device 1101 receives the answer from eachremote device including the reference devices R₁-R₄, devices X anddevices Y, and decodes the positional information of each remote deviceand stores the distances of the positional information in main memory307. From the stored distance information, processor 305 of device 1101determines the position of each device using a triangulation process asseen in step 1207. All positions are then displayed on the display 313of the local device 1101 so that the user of the local device canassociate each remote device on the screen with a remote devicephysically located in the conference room 1100.

[0164] According to a preferred embodiment, the local device 1101 usestriangulation information to determine which remote devices are outsidea boundary formed by reference devices R₁-R₄ and uses this informationto display only those devices within the boundary. Thus, according tothis embodiment, the local device 1101, identifies the remote devices Ylocated in rooms 1200 and 1300 of FIG. 11 and does not display thesedevices on the display 313 of the local device 1101.

[0165] With the remote devices located within conference room 1100displayed on the display 313 of the local device 1101, the user enablescommunications with a remote device viewed in physical space of theconference room 1100 by selecting a corresponding position on thedisplay in order to, as shown in step 1209. According to one embodiment,the display 313 has touch screen capabilities that allow the user toselect a remote device by contacting the display with a pointing device,for example. If the user of the local device 1101 selects a positionlocated on the display of the local device, then the local device 1001enables communications with that device as shown in step 1215.

[0166] As with other embodiments, positional information on enabledlinks is updated as shown in step 1217 and loop 507 of FIG. 12. If theuser does not select a position on the display screen, thecommunications link associated with the unselected device is blockedfrom data communications as in step 1211 and positional information forblocked links is updated in step 1213. Also, as with other embodiments,the local device 1101 periodically looks for new devices and updatescommunications links as shown by connection C FIG. 12.

[0167] According to a preferred embodiment, display 313 indicates whichremote devices are enabled as positional information is updated in steps1213 and 1217. Thus, as seen in FIG. 11, remote devices for whichcommunications are enabled may be indicated by circling the remotedevices. As the remote devices X move around conference room 1100, theuser of local device 1101 can keep track of which devices communicationsare enabled for by viewing the circled Xs on display 313.

[0168] Thus, according to the embodiment of the present invention shownin FIGS. 6, 7, 9, and 12, the local device 1101 displays a graphical mapof the position of remote devices in relation to the local device andenables communications based on local user's selection of a remotedevice on the map. As the positions are determined based on positionaldata that includes distances between the remote devices, devices may beenabled with the local device based on their distance to the localdevice 1101 without the need for the user of the local device 1101selecting from among a list of remote devices as discussed in thebackground section above.

[0169] According to a preferred embodiment of the present invention,communications links enabled by any of the processes described may be asecure communications using encryption methods such as the methodsdescribed in the text entitled HOW THE INTERNET WORKS, MillenniumEdition, Preston Gralla, Macmillan Computer Publishing, Indianapolis1999, the contents of which are incorporated by reference in theirentirety.

[0170]FIG. 13 describes an exemplary process for providing a securedcommunications link using public key cryptography in accordance with apreferred embodiment of the present invention. In step 1301, the localdevice 1001 transmits a request for secured communications to enabledremote devices. The request includes public key of the local devicerequesting the secured communications. The public key is a key that isshared with any remote device and is used by the remote device toencrypt a data communication intended for the local device.

[0171] In step 1303, the enabled remote devices receive the request forsecured communications and the public key of the local device. Eachenabled remote device then decodes the public key in step 1305 and usesthe public key to encrypt any message that the remote device intends forthe local device in step 1307. As seen in step 1307, encryption isaccomplished by applying the public key of the local device and themessage to any one of a variety of known encryption algorithms. Theencrypted message is then transmitted from the enabled remote device tothe local device.

[0172] In step 1307, the local device receives the encrypted messagethat is unintelligible. Any device that may intercept the encryptedmessage will not be able to decrypt the message even if the interceptingdevice has the public key of the local device because a private key thatonly the local device has is needed to decrypt the unintelligiblemessage.

[0173] In step 1309, the local device obtains its private key frommemory and decrypts the encrypted message using the private key. Thus,secure communications can be provided for any one of the discussedembodiments for enabling communications based on distance informationdescribed above. In addition, it is to be understood that methods ofguaranteeing the source of a particular message, such as digitalcertificates and other means of authentication may also be applied tothe present invention.

[0174] FIGS. 14 to 16 show the remote devices 410 ₁, . . . , 410 _(N)according to preferred embodiments of the present invention. Inparticular, FIG. 14 shows a UWB tag 1400 configured as a transmitter;FIG. 15 shows a UWB tag 1500 configured as a receiver; and FIG. 16 showsa UWB tag 1600 configured as a transceiver.

[0175] As shown in FIG. 14, the UWB tag 1400 used for transmittingincludes an antenna 1405, a physical layer (PHY) 1410, a media accesscontroller (MAC) 1415, a memory 1420, a host controller interface (HCI)1425, and a power supply 1430. In the UWB tag 1400, the various elementsoperate as follows.

[0176] The antenna 1405 transmits a UWB signal as provided to it fromthe PHY 1410, which prepares the signal for transmission in a mannersimilar to that disclosed above for the RF PMD 120 and the digital PMD130 shown in FIG. 1. In an embodiment where the UWB tag 1400 acts onlyas a transmitter, the PHY 1410 can be reduced in complication ascompared to the RF PMD 120 and the digital PMD 130 by eliminating allcircuitry relating to receiving functions. Furthermore, if only alimited kind of signal will need to be transmitted, the PHY 1410 may befurther simplified such that it only supports that limited type ofsignal.

[0177] The MAC 1415 serves as the interface between the UWB wirelesscommunication functions implemented by the PHY 1410 and the datacontained in the memory 1420. The MAC 1415 essentially translates thedata stored in the memory 1420 into a format that the PHY 1410 cantransmit via the antenna 1405. Given the limited functions that must beperformed by the MAC 1415, it is significantly reduced in complexity ascompared to the MAC 150 shown in FIG. 1. In alternate embodiments theMAC 1415 could be eliminated altogether and the memory 1420 could beloaded with data already in the proper form for the PHY 1410 to use.

[0178] The memory 1420 holds the information that will be transmitted bythe UWB tag 1400. For example, it may include tag ID data, date ofplacement of the tag, information about what the tag is associated with(person, product, shipment, etc.), or any other desirable information.In the preferred embodiment memory 1420 is a static memory device, suchas an EPROM, EEPROM, etc.

[0179] The HCI 1425 serves as an interface for providing data to thememory 1420 from an external source. It could connect to a bar codereader if the tag 1400 includes simple identification information, acomputer output if it receives more complicated information, an internalprocessor if the tag 1400 is contiguous with a remote device such as aPDA, etc.

[0180] In alternate embodiments where the data in the memory 1420 neednot be changed during the lifetime of the UWB tag (e.g., anidentification tag), the memory 1420 may be a read-only memory and theHCI 1425 may be eliminated.

[0181] The power supply 1430 provides the necessary power required tooperate the elements of the UWB tag 1400. It is preferably a batterypower source that is configured in a fashion to extend its lifetime aslong as possible. However, alternate sources may be used provided theycould meet power and functional lifetime requirements.

[0182] As shown in FIG. 15, the UWB tag 1500 for receiving includes anantenna 1405, a physical layer (PHY) 1510, a media access controller(MAC) 1515, a memory 1520, a host controller interface (HCI) 1525, and apower supply 1430. In the UWB tag 1500 the various elements operate asfollows.

[0183] The antenna 1405 receives a UWB signal, transforms it into anelectrical or optical signal, and as provides to it from the PHY 1510,which demodulates the signal and extracts the data from it in a mannersimilar to that disclosed above for the RF PMD 120 and the digital PMD130 shown in FIG. 1. In an embodiment where the UWB tag 1500 acts onlyas a receiver, the PHY 1510 can be reduced in complication as comparedto the RF PMD 120 and the digital PMD 130 by eliminating all circuitryrelating to transmitting functions. Furthermore, if only a limited kindof signal will need to be received, the PHY 1510 may be furthersimplified such that it only supports that limited type of signal.

[0184] The MAC 1515 serves as the interface between the UWB wirelesscommunication functions implemented by the PHY 1410 and the data used bythe memory 1520 and HCI 1525. The MAC 1515 essentially translates thedata received from the PHY 1510 into a format that the memory 1520 orHCI 1525 can use. Given the limited functions that must be performed bythe MAC 1515, it is significantly reduced in complexity as compared tothe MAC 150 shown in FIG. 1. In alternate embodiments the MAC 1515 couldbe eliminated altogether and the memory 1520 or the HCI 1525 can receiveand use the data in form received from the PHY 1510.

[0185] The memory 1520 holds information received by the UWB tag 1500.For example, it may include local or remote device ID data, operator ID,time or date information, operational instructions, or any otherdesirable information. In the preferred embodiment memory 1520 may beany desirable static memory device, such as an EPROM, EEPROM, etc.

[0186] The HCI 1525 serves as an interface for taking data from thememory 1520 and providing it to an outside device (not shown). Thisoutside device could be a PDA, a computer, a display device, or thelike. The HCI 1525 could include timing, data conversion functions, orthe like, as necessary.

[0187] In alternate embodiments where the information received by theUWB tag 1500 may be sent directly to the outside device, e.g., to soundan alarm or change a display, the memory 1520 can be eliminated. Inembodiments where the data can be used unchanged, it may also bepossible to eliminate the HCI 1525 and send information directly fromthe MAC 1515 to an outside device.

[0188] The power supply 1530 provides the necessary power required tooperate the elements of the UWB tag 1500. It is preferably a batterypower source that is configured in a fashion to extend its lifetime aslong as possible. However alternate sources may be used provided theymeet required power and functional lifetime requirements.

[0189] As shown in FIG. 16, the UWB tag 1600 for transmitting orreceiving includes an antenna 1405, a switch 1607, a physical layer(PHY) 1610, a media access controller (MAC) 1615, a memory 1620, a hostcontroller interface (HCI) 1625, and a power supply 1430. The PHY 1610further includes receiver circuitry 1611, transmitter circuitry 1612,and a PHY later conversion protocol (PLCP) 1613. In the UWB tag 1400,the various elements operate as follows.

[0190] The antenna 1405 operates to transmit or receive a UWB signaldepending upon whether it is in a transmit or receive mode. In eithercase, the PHY layer conversion protocol 1613 performs a function similarto the PHY layer conversion protocol 140 in FIG. 1.

[0191] In a receive mode, the switch 1607 connects the antenna 1405 tothe receiver circuitry 1611. The PHY 1610 then handles the receipt ofthe incoming signal in a manner similar to that disclosed above for theRF PMD 120 and the digital PMD 130 shown in FIG. 1 with the receivercircuitry 1611 including the functions of the receiver front end 122,demodulator 124, and receiver baseband 134. In an embodiment where onlya limited kind of signal will need to be received, the receivercircuitry 1611 may be simplified such that it only supports that limitedtype of signal.

[0192] In a transmit mode, the switch 1607 connects the antenna 1405 tothe transmitter circuitry 1612. The PHY 1610 then prepares the signalfor transmission in a manner similar to that disclosed above for the RFPMD 120 and the digital PMD 130 shown in FIG. 1, with the transmittercircuitry 1612 including the functions of the transmitter front end 126,modulator 128, and transmitter baseband 134. In an embodiment where onlya limited kind of signal will need to be transmitted, the transmittercircuitry 1612 may be simplified such that it only supports that limitedtype of signal.

[0193] The MAC 1615 serves as the interface between the UWB wirelesscommunication functions implemented by the PHY 1610 and the datacontained in the memory 1620. It preferably operates as shown above forthe MAC 1415 in FIG. 14 an d the MAC 1515 in FIG. 15. Although the MAC1615 has more functions than either the MACs 1415 or 1515, it is stillreduced in complexity as compared to the MAC 150 shown in FIG. 1. Inalternate embodiments the MAC 1615 could be eliminated altogether andthe memory 1620 could be loaded with data already in the proper form forthe PHY 1610 to use, and data could be sent on to an outside devicewithout storing it.

[0194] The memory 1620 holds the information that will be transmitted bythe UWB tag 1600 or holds information received by the UWB tag 1600. Inthe preferred embodiment memory 1620 is a static memory device, such asan EPROM, EEPROM, etc.

[0195] The HCI 1625 serves as an interface between the memory 1620 andany outside devices, as shown above for the HCI 1425 of FIG. 14 or theHCI 1525 of FIG. 15.

[0196] In alternate embodiments where the data in the memory 1620 neednot be changed during the lifetime of the UWB tag (e.g., anidentification tag), and no incoming data need be stored, the memory1620 may be a read-only memory and the HCI 1625 may be eliminated.

[0197] The power supply 1430 provides the necessary power required tooperate the elements of the UWB tag 1600. It is preferably a batterypower source that is configured in a fashion to extend its lifetime aslong as possible. However alternate sources may be used provided thatthey can meet power and functional lifetime requirements.

[0198] One limitation of each of these designs that operates as areceiver is that they require either constant or periodic operation tomonitor for incoming signals. These operations occur regardless of datatraffic. This can have a detrimental effect on the power supply for thedevice.

[0199] In an effort to correct this problem and to extend the life ofthe power supply in a UWB tag, the current inventor proposes the use ofboth UWB and RF tags on the same device. FIGS. 17 to 21 are blockdiagrams showing various embodiments of this aspect of the invention.

[0200]FIG. 17 shows a combined UWB-RF tag according to a first preferredembodiment of the present invention. As shown in FIG. 17, the UWB-RF tag1700 includes UWB circuitry 1705, RF circuitry 1710, a UWB-RF interface1715, and a power supply 1720.

[0201] The UWB circuitry 1705 is preferably of the sort described abovewith respect to FIGS. 14 to 16. The RF circuitry 1710 is preferably of akind generally known, such as that shown, for example, in U.S. Pat. No.6,107,910 to Nysen.

[0202] The UWB-RF interface 1715 connects the UWB circuitry 1705 withthe RF circuitry 1710. The power supply 1720 provides power to the UWBcircuitry (and to the RF circuitry 1710 and UWB-RF interface 1715, ifnecessary). It is preferably chosen to have characteristics that willmaximize its effective lifetime given the operational requirements ofthe UWB-RF tag 1700.

[0203] In this design, the functions of an ID tag are shared between theUWB circuitry 1705 and the RF circuitry 1710. For example, the UWBcircuitry 1705 could handle the transmission of data and the RFcircuitry 1710 could handle the reception of data; the RF circuitry 1710could be used for initial contact with a local device (as shown in FIG.4) and the UWB circuitry 1705 could be used for all other contact; theRF circuitry 1710 could be used generally with the UWB circuitry 1705being used only when interference was too great; or any other desirableconfiguration could be used.

[0204] The UWB-RF interface 1715 need only be as complicated asnecessary, and may be as simple as a signal line, or may even beeliminated altogether if the functions of the two elements can beperformed without direct contact. However, in alternate embodiments theUWB-RF interface 1715 could perform more complicated operations and mayinclude more complicated logic such as an ASIC, a CPU, or the like.

[0205]FIG. 18 shows a combined UWB-RF tag according to a secondpreferred embodiment of the present invention. As shown in FIG. 18, theUWB-RF tag 1800 includes UWB circuitry 1805, RF circuitry 1810, a UWB-RFinterface 1815, a power supply 1820, and a switch 1825 connected betweenthe UWB circuitry 1805 and the power supply 1820. As above, the UWBcircuitry 1805 is preferably of the sort described above with respect toFIGS. 14 to 16, while the RF circuitry 1810 is preferably of a kindgenerally known.

[0206] The RF circuitry 1810 in this embodiment is preferably of a sortthat is run on RF power and does not require its own separate powersupply. This is accomplished by using transmitted RF signals to charge acapacitor (not shown) in the RF circuitry 1810. The charge on thecapacitor is then used to run the RF circuitry 1810 and is maintained bythe transmitted RF signals.

[0207] The RF circuitry 1810 is then used to turn on the UWB circuitry1805 by passing the UWB-RF interface 1815 a signal that is used tooperate the switch 1825 that connects the UWB circuitry 1805 to thepower supply 1820. In the current embodiment a signal is simply passedthrough the UWB-RF interface 1815 from the RF circuitry 1810 to controlthe switch 1825. However, in alternate embodiments a more complicatedoperation may be performed on the signal from the RF circuitry todetermine whether the switch 1825 should be opened or closed.

[0208] Since the RF circuitry 1810 in this embodiment operates on RFpower and so does not require it's own separate power source, the RFcircuitry 1810 can be operated continually without any negative impacton the life of the power supply 1820 for the UWB-RF tag 1800. The UWBcircuitry 1805 is thus turned on only when it is needed, and sominimizes its power consumption.

[0209] In operation, a local device (See element 405 in FIG. 4) willsend a message to the UWB-RF tag 1800 using RF signals. The RF circuitry1810 will receive the signals, charge up, and then close the switch1825, connecting the UWB circuitry 1805 to the power supply 1820. Thiswill cause the UWB circuitry 1805 to power up, at which point it canperform whatever function is needed based on the design of the system.

[0210] In this embodiment the UWB circuitry 1805 will send to the localdevice a set of identification information. However, in alternateembodiments this can be a different or more complicated operation. Forexample, the RF circuitry 1810 could receive information from the localdevice regarding what function the UWB circuitry 1805 should perform.This information could then be passed on to the UWB circuitry 1805through the UWB-RF interface 1815, and the function performed by the UWBcircuitry 1805.

[0211] Once the UWB circuitry 1805 has completed its operation, theswitch 1825 will be opened, shutting off the UWB circuitry 1805 bydisconnecting it from the power supply 1820 until the RF circuitry 1810again connects it. In this way the UWB circuitry 1805 will not depletethe power supply 1820 except when it is specifically performingfunctions requested by a local device.

[0212] This embodiment is advantageous because the RF circuitry 1810 isused to detect a request for information from the tag 1800, while theUWB circuitry 1805 is used act on that request. By using the RFcircuitry 1810 to continually monitor for requests from a central localdevice the tag 1800 gains the advantage of low power consumption. Andsince the local device may well have fewer power restrictions (e.g., itmay be plugged into a wall socket rather than operating on batterypower), it can send out a stronger signal that can be more easily pickedup by the RF circuitry 1810.

[0213] But by using the UWB circuitry 1805 for data transmission thedevice realizes the advantages in high data rate transmission at lowpower consumption at the tag end, as well as good UWB performancethrough cluttered environments. In other words, the combined UWB-RF tag1800 gets the primary advantages of RF and UWB tags while avoiding theprimary disadvantages of each.

[0214] This combined UWB-RF tag 1800 can also be easy to design. In itssimplest form a conventionally-available RF tag can be connected as thecontrol of a, switch on a UWB tag. In this way the combined tag can bemade more easily and cheaply without the need to redesign either the UWBcircuitry 1805 or the RF circuitry 1810.

[0215]FIG. 19 shows a combined UWB-RF tag according to a third preferredembodiment of the present invention. As shown in FIG. 19, the UWB-RF tag1900 includes UWB circuitry 1905, RF circuitry 1910, a UWB-RF interface1915, a power supply 1920, and a switch 1925 connected between the UWBcircuitry 1905 and the power supply 1920. The UWB-RF interface 1915further includes a first frequency scaler 1930. The UWB circuitry 1905is preferably of the sort described above with respect to FIGS. 14 to16, while the RF circuitry 1910 is preferably of a kind generally known.

[0216] The UWB-RF tag 1900 of FIG. 19 operates exactly like the UWB-RFtag 1800 in FIG. 18, except for the inclusion of the first frequencyscaler 1930. In this embodiment, elements whose last two digitscorrespond to elements from FIG. 18 perform functions similar to thosein the second preferred embodiment.

[0217] The first frequency scaler 1930 is formed in the UWB-RF interface1915 between the UWB circuitry 1905 and the RF circuitry 1910. Itreceives the signal frequency f₀ of the RF signal received by the RFcircuitry 1910 and scales it by a first scaling factor N/M. The scaledfrequency is then used by the UWB circuitry 1905 to set the pulserepetition frequency for UWB operation PRF_(UWB), such that:$\begin{matrix}{{PRF}_{UWB} = {\frac{N}{M} \cdot {f_{0}.}}} & (5)\end{matrix}$

[0218] The first scaling factor N/M is determined by dividing an integerN by an integer M. In embodiments where N=1, the first scaling factorcan be reduced to 1/M; and in embodiments where M=1, the first scalingfactor can be reduced to N. In embodiments where N=M=1, the firstscaling factor becomes 1 and the first frequency scaler 1930 can beeliminated.

[0219] In alternate embodiments the switch 1925 could also beeliminated. In this case the RF circuitry 1910 may simply provide thesignal frequency f₀, or may perform some additional function.

[0220]FIG. 20 shows a combined UWB-RF tag according to a fourthpreferred embodiment of the present invention. As shown in FIG. 20, theUWB-RF tag 2000 includes UWB circuitry 2005, RF circuitry 2010, and aUWB-RF interface 2015. The UWB-RF interface 2015 further includes asecond frequency scaler 2035, a memory 2040, and a mixer 2045. The mainUWB circuitry 2030 is preferably of the sort described above withrespect to FIGS. 14 to 16, while the RF circuitry 2010 is preferably ofa kind generally known.

[0221] The UWB-RF tag 2000 of FIG. 20 operates exactly like the UWB-RFtag 1700 in FIG. 17, except for the inclusion of the second frequencyscaler 2035. In this embodiment elements whose last two digitscorrespond to elements from FIG. 17 perform functions similar to thosein the first preferred embodiment.

[0222] The second frequency scaler 2035 is connected between the RFcircuitry 2010 and the mixer 2045. It receives the signal frequency f₀of the RF signal received by the RF circuitry 2010 and scales it by asecond scaling factor of P/Q.

[0223] The second scaling factor P/Q is determined by dividing aninteger P by an integer Q. In embodiments where P=1, the second scalingfactor can be reduced to 1/Q; and in embodiments where Q=1, the secondscaling factor can be reduced to P. In embodiments where P=Q=1, thesecond scaling factor becomes 1 and the second frequency scaler 2035 canbe eliminated.

[0224] The scaled frequency is then combined in the mixer 2045 with asignal received from the memory 2040. The memory 2040 provides a datasignal that is used to form the incoming UWB radio frequency signalRF_(UWB) for the UWB circuitry out of the incoming radio frequency RFsignal received by the RF circuitry 2045.

[0225] The data from the memory 2040 will tell the mixer 2045 whatportions of the incoming RF signal RF will be kept to form the UWB RFsignal RF_(UWB). This can be used in a way that allows the signal to becreated with pulse position modulation (PPM) as seen, for example, inFIGS. 23A to 23C. Alternately the signal RF_(UWB) could be created as abi-phase UWB signal as shown in FIGS. 24A to 24C. Finally, the signalcould be encoded using chirping by modifying the mixer 2045 accordingly.

[0226] The UWB RF signal RF_(UWB) is then sent from the mixer 2045 tothe UWB circuitry 2005 where it is used for general UWB operation.However, since it was derived from the signal frequency f₀ of the RFsignal received by the RF circuitry 1910, the UWB RF signal RF_(UWB)will be coherent with the incoming RF signal RF.

[0227]FIG. 21 shows a combined UWB-RF tag according to a fifth preferredembodiment of the present invention. As shown in FIG. 21, the UWB-RF tag2100 includes UWB circuitry 2105, RF circuitry 2110, a UWB-RF interface2115, a power supply 2120, and a switch 2125 connected between the UWBcircuitry 2105 and the power supply 2120. The UWB-RF interface 2115further includes a second frequency scaler 2135, a memory 2140, and amixer 2145. The main UWB circuitry 2130 is preferably of the sortdescribed above with respect to FIGS. 14 to 16, while the RF circuitry2110 is preferably of a kind generally known.

[0228] The operation of the UWB-RF tag 2100 of FIG. 21 is the same asthe UWB-RF tag 1800 of FIG. 18 combined with the UWB-RF tag 2000 of FIG.20. In this embodiment elements whose last two digits correspond toelements from FIGS. 18 and 20 perform functions similar to those in thesecond and fourth preferred embodiments.

[0229] The tag 2100 uses the RF circuitry 2110 to both control thesupply of power to the UWB circuitry 2105 and to provide the frequencysignal f₀ to allow the UWB-RF interface 2115 to create the UWB RF signalRF_(UWB).

[0230]FIG. 22 shows a combined UWB-RF tag according to a sixth preferredembodiment of the present invention. As shown in FIG. 22, the UWB-RF tag2200 includes UWB circuitry 2205, RF circuitry 2210, a UWB-RF interface2215, a power supply 2220, and a switch 2225 connected between the UWBcircuitry 2205 and the power supply 2220. The UWB-RF interface 2215further includes a first frequency scaler 2230, a second frequencyscaler 2235, a memory 2240, and a mixer 2245. The main UWB circuitry2230 is preferably of the sort described above with respect to FIGS. 14to 16, while the RF circuitry 2210 is preferably of a kind generallyknown.

[0231] The operation of the UWB-RF tag 2200 of FIG. 22 is the same asthe UWB-RF tag 1900 of FIG. 19 combined with the UWB-RF tag 2000 of FIG.20. The tag 2200 uses the RF circuitry 2210 to both control the supplyof power to the UWB circuitry 2205 and to provide the frequency signalf₀ to allow the UWB-RF interface 2215 to create both the UWB pulsereference frequency PRF_(UWB) and the UWB RF signal RF_(UWB).

[0232] In this embodiment elements whose last two digits correspond toelements from FIGS. 19 and 20 perform functions similar to those in thethird and fourth preferred embodiments.

[0233]FIGS. 23A to 24C show two embodiments of how a UWB RF signalRF_(UWB) can be generated to be coherent with the incoming RF signal RF.FIGS. 23A to 23C show an embodiment in which pulse position modulation(PPM) is used. FIGS. 24A to 24C show an embodiment in which bi-phasemodulated signals are used.

[0234]FIG. 23A shows the RF signal RF received by the RF circuitry 2110,2210 and passed on to the UWB-RF interface 2115, 2215. The RF signal RFis preferably a periodic signal operating at a given frequency f₀.

[0235]FIG. 23B shows the data signal from the memory 2140, 2240 insideof the UWB-RF interface 2115, 2215. The data signal is preferably astream of 1's and 0's that will operate in the mixer 2145, 2245 toeither pass the RF signal RF or cancel it out. Most particularly thedata signal can be considered a stream of pulses with a value of “1”separated from each other by set distances, during which the value ofthe signal is “0.” One distance Δt is shown in FIG. 23B

[0236]FIG. 23C shows the UWB RF signal RF_(UWB) output from the mixer2145, 2245. As shown in FIG. 23C, when the data signal of FIG. 23B is“1” the mixer 2145, 2245 passes the RF signal RF unchanged to the UWB RFsignal RF_(UWB). When the data signal is “0” the mixer 2145, 2245cancels the RF signal RF, allowing the UWB RF signal RF_(UWB) to pass asa ground or reference voltage.

[0237] In the embodiment shown in FIGS. 23A to 23C, the distance Δtbetween pulses in the data signal can be varied to encode informationinto the UWB RF signal RF_(UWB). In other words, the UWB RF signalRF_(UWB) is encoded using PPM.

[0238]FIG. 24A shows the RF signal RF received by the RF circuitry 2110,2210 and passed on to the UWB-RF interface 2115, 2215. The RF signal RFis preferably a periodic signal operating at a given frequency f₀.

[0239]FIG. 24B shows the data signal from the memory 2140, 2240 insideof the UWB-RF interface 2115, 2215. The data signal is preferably astream of pulses as a set distance from each other with values “1” and“−1,” with the area between the pulses being at a value of “0,” thatwill operate in the mixer 2145, 2245 to pass the RF signal RF unchanged,invert the RF signal RF and pass the inverted signal, or cancel it out.

[0240]FIG. 24C shows the UWB RF signal RF_(UWB) output from the mixer2145, 2245. As shown in FIG. 24C, when the data signal of FIG. 24B is“1” the mixer 2145, 2245 passes the RF signal RF unchanged to the UWB RFsignal RF_(UWB). When the data signal is “−1” the mixer 2145, 2245passes the RF signal RF inverted to the UWB RF signal RF_(UWB). When thedata signal is “0” the mixer 2145, 2245 cancels the RF signal RF,allowing the UWB RF signal RF_(UWB) to pass as a ground or referencevoltage.

[0241] In the embodiment shown in FIGS. 24A to 24C, the polarity of thepulses of the data signal can be varied to encode information into theUWB RF signal RF_(UWB). In other words, the UWB RF signal RF_(UWB) isencoded using bi-phase modualtion.

[0242] In alternate embodiments other methods of encoding data into theUWB RF signal RF_(UWB) can be used. For example, each wavelet may beconfigured to communicate q bits, where M≧2^(q). For example, fourshapes may be configured to communicate two bits, such as withquadrature phase or four-level amplitude modulation. In anotherembodiment of the present invention, each wavelet is a “chip” in a codesequence, where the sequence, as a group, communicates one or more bits.The code can be M-ary at the chip level, choosing from M possible shapesfor each chip.

[0243] At the chip, or wavelet level, embodiments of the presentinvention produce UWB waveforms. The UWB waveforms are modulated by avariety of techniques including but not limited to: (i) bi-phasemodulated signals (+1, −1), (ii) multilevel bi-phase signals (+1, −1,+a1, −a1, +a2, −a2, . . . , +aN, −aN), (iii) quadrature phase signals(+1, −1, +j, −j), (iv) multi-phase signals (1, −1, exp(+jπ/N),exp(−jπ/N), exp(+jπ2/N), exp(−jπ2/N), . . . , exp(+jπ(N-1)/N),exp(−jπ(N-1)/N)), (v) multilevel multi-phase signals (a_(i)exp(j2πβ/N)|a_(i) ε{1, a1, a2, . . . , aK}, βε{0, 1, . . . , N-1}), (vi)frequency modulated pulses, (vii) pulse position modulation (PPM)signals (possibly same shape pulse transmitted in different candidatetime slots), (viii) M-ary modulated waveforms g_(B), (t) with B_(i) ε{1,. . . , M}, and (ix) any combination of the above waveforms, such asmulti-phase channel symbols transmitted according to a chirpingsignaling scheme. In the case of chirping, this function may beperformed in the UWB-RF interface 2115, 2215, more preferably at themixer 2145, 2245.

[0244] The present invention, however, is applicable to variations ofthe above modulation schemes and other modulation schemes (e.g., asdescribed in Lathi, “Modern Digital and Analog Communications Systems,”Holt, Rinehart and Winston, 1998, the entire contents of which isincorporated by reference herein), as will be appreciated by thoseskilled in the relevant art(s).

[0245] Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. For example, anyone of the above described processes for enabling device functions andcommunications may be modified by use of signal strength informationprovided in any known manner. It is also understood that the presentinvention should not be limited to ID tags, but could be used for othercommunications devices as well, e.g., PDAs, stationary informationkiosks, etc. It is therefore to be understood that within the scope ofthe appended claims, the invention may be practiced otherwise than asspecifically described herein.

We claim:
 1. A combined ultrawide bandwidth-radio frequency (UWB-RF)remote identification tag, comprising: ultrawide bandwidth (UWB)circuitry for receiving or transmitting UWB signals; radio frequency(RF) circuitry for receiving or transmitting RF signals; and interfacecircuitry formed between the RF circuitry and the UWB circuitry.
 2. Acombined UWB-RF remote identification tag, as recited in claim 1,further comprising: a power supply for providing power to the UWBcircuitry; and a switch connected between the power supply and the UWBcircuitry, wherein the interface circuitry controls the operation of theswitch based on a signal received from the RF circuitry.
 3. A combinedUWB-RF remote identification tag, as recited in claim 1, wherein theUWB-RF interface further comprises a first scaler for receiving afrequency signal from the RF circuitry, scaling it by a first scalingfactor N/M, and providing a first scaled frequency to the UWB circuitry,and wherein N and M are integers.
 4. A combined UWB-RF remoteidentification tag, as recited in claim 3, further comprising: a powersupply for providing power to the UWB circuitry; and a switch connectedbetween the power supply and the UWB circuitry, wherein the interfacecircuitry controls the operation of the switch based on a signalreceived from the RF circuitry.
 5. A combined UWB-RF remoteidentification tag, as recited in claim 3, wherein the scaled frequencyis used by the UWB circuitry as a pulse repetition frequency.
 6. Acombined UWB-RF remote identification tag, as recited in claim 1,wherein the UWB-RF interface further comprises: a second scaler forreceiving the frequency signal from the RF circuitry, scaling it by asecond scaling factor P/Q, and providing a second scaled frequency tothe UWB circuitry; a memory device for providing a data signal; and amixer for mixing the second scaled frequency with the data signal toform a UWB radio frequency signal, wherein P and Q are integers.
 7. Acombined UWB-RF remote identification tag, as recited in claim 6,further comprising: a power supply for providing power to the UWBcircuitry; and a switch connected between the power supply and the UWBcircuitry, wherein the interface circuitry controls the operation of theswitch based on a signal received from the RF circuitry.
 8. A combinedUWB-RF remote identification tag, as recited in claim 1, wherein theUWB-RF interface further comprises: a first scaler for receiving afrequency signal from the RF circuitry, scaling it by a first scalingfactor N/M, and providing a first scaled frequency to the UWB circuitry;a second scaler for receiving the frequency signal from the RFcircuitry, scaling it by a second scaling factor P/Q, and providing asecond scaled frequency to the UWB circuitry; a memory device forproviding a data signal; and a mixer for mixing the second scaledfrequency with the data signal to form a UWB radio frequency signal, andproviding the UWB radio frequency signal to the UWB circuitry, whereinN, M, P and Q are integers.
 9. A combined UWB-RF remote identificationtag, as recited in claim 8, further comprising: a power supply forproviding power to the UWB circuitry; and a switch connected between thepower supply and the UWB circuitry, wherein the interface circuitrycontrols the operation of the switch based on a signal received from theRF circuitry.
 10. A method of responding to an incoming signal,including: receiving an incoming RF signal; processing the incoming RFsignal to generate an activation signal; activating a UWB circuit inresponse to the activation signal; performing a UWB function with theUWB circuit after the UWB circuit is activated.
 11. A method ofresponding to an incoming signal, as recited in claim 10, wherein theUWB function is UWB data transmission.
 12. A method of responding to anincoming signal, as recited in claim 10, wherein the UWB function is UWBdata reception.
 13. A method of responding to an incoming signal, asrecited in claim 10, wherein the step of activating the UWB circuit isperformed by having the activation signal connect the UWB circuit to apower supply.
 14. A method of responding to an incoming signal, asrecited in claim 10, further including shutting off the UWB circuitafter the UWB function is performed.